Thermal Characterization of Vinyl Acetate—Ethylene Copolymers

Copolymers of vinyl acetate and ethylene were prepared by emulsion polymerization using ammonium persulphate and sodium metabisulphite as initiators in presence of cyclohexane. Several copolymer samples were prepared by changing initial pressure of ethylene from 100 to 250 psi. The copolymer composition was determined by ¹H-NMR and thermogravimetric analysis in nitrogen atmosphere.This revised version was published online in November 2005 with corrections to the Cover Date.     

Spegtrophotometrig Determination of α -Tocopherol Acetate in Soft Capsules

Abstract

Two spectrophotometric methods have been described for the determination of α -tocopherol acetate (vitamin E) in soft capsules. The first method applies the orthogonal function method under least squares. The quadratic coefficients calculated over the wavelength range 277 - 304 nm at 4-nm intervals in chloroform were reproducible and independent of ethyl oleate concentration. The second method applies the second derivative (D₂) to correct for irrelevant absorbance due to ethyl oleate The peak trough amplitude at 271 - 287 nm was in linear correlation to the concentration of vitamin E. The recoveries obtained using the proposed methods agreed with those obtained using the official proceduce.     

Fries Rearrangement of Phenyl Acetate over Solid Acid Catalyst

A silica-supported zirconium based solid acid (ZS) has been used as catalyst for the Fries rearrangement of phenyl acetate (PA). The catalyst showed a higher PA conversion activity and a much higher selectivity for o-hydroxyacetophenone (o-HAP) than for strongly acidic zeolite catalysts. The supported catalyst was characterized by XRD,IR,XPS,pyridine-TPD and the surface area measurements. The catalytic properties were influenced significantly by pretreatment temperature.     

1,3-Dipolar Cycloaddition Reaction between Vinyl Acetate and N-Alkyl Hydroxypyridinium Halide

The 1, 3-dipolar cycloaddition reaction between 3-hydroxypyridiniun betaines and a great variety of dipolarphiles, such as CH2=CH-CN, CH2=CH-COCH3, CH2=CH-COOCH3, CH2=CH(CH3)-COOCH3 were first investigated by Alan R. Katritzky et al.1-3. Generally, the olefinic dipolarphiles containing a strongly electron-withdrawing group are more active. Vinyl acetate 2 is an electron-rich dipolarphile, it is very difficult to carry out 1, 3-dipolar cycloaddition reaction with 3-hydropyridin…     

α,α-Dicyanoethyl Acetate. A Reagent for Selective N-Acetylation

N-Aoetylation is one of the classical methods for protection of primary and secondary amino groups.¹ While there is a lavish repertoire of reagents and conditions available for its execution, few exhibit the desirable feature of discriminative action between hydroxyl and anino functions. This communication disseminates the use of α,α-dicyanoethyl acetate (1) as a selective N-acetylation agent.     

Preparation and Performance of Polysulfone‐Cellulose Acetate Blend Ultrafiltration Membrane

In the development of high performance polymeric membranes, it is essential to design the molecular and morphological characteristics for specific applications. Polysulfone and cellulose acetate of blend membranes with various concentration of polymer pore former, PEG600 were prepared by phase inversion technique and used for ultrafiltration. Polymer blend composition, additive concentration, and casting conditions were optimized. The blend membranes were characterized in terms of compaction, pure water flux, water content, hydraulic resistance and separation of dextran studies. Surface morphology of the embranes was analyzed using scanning electron microscopy at different magnifications. Further, the characterized membranes were attempted for treatment of distillery effluents after secondary treatment and the results are discussed in detail.     

Volumetric and Acoustic Studies of Binary Liquid Mixtures of Dipropylene Glycol Dimethyl Ether with Methyl Acetate, Ethyl Acetate and n-Butyl Acetate in the Temperature Range T = (288.15, 293.15, 298.15, 303.15, and 308.15) K

Densities and ultrasonic speeds have been measured over the whole composition range for binary liquid mixtures of dipropylene glycol dimethyl ether, CH₃(OC₃H₆)₂OCH₃, with methyl acetate, ethyl acetate, and n-butyl acetate using an Anton Paar DSA 5000 M density and speed sound analyzer at T = (288.15, 293.15, 298.15, 303.15, and 308.15) K and atmospheric pressure in order to evaluate the behavior of these binaries. From these data excess the molar volume, $ V_{m}^{\text{E}} $ , and deviation in isentropic compressibility, ?κ _S , have been calculated. These excess properties have been fitted with the Redlich–Kister type polynomial equation to get their coefficients and standard deviations which provide a base for discussing the forces operating in solutions.     

Electroreduction of Mo(VI) Compounds in Ammonium–Acetate Solutions

The kinetics of cathodic reactions in ammonium acetate solutions proposed for electrodeposition of metallic molybdenum was studied. The reduction of molybdenum compounds in the oxidation state +6 was found to occur stepwise according to the scheme Mo(VI) → Mo(V) → Mo(III). The waves observed on the polarograms are complicated by adsorption effects. The reduction of molybdenum to the metallic state is possible only at high negative potentials of the cathode; under the polarographic analysis conditions, this wave was not recorded. The deposit that formed on the surface of the solid cathode during cathodic polarization (i = 0.5 A cm^–2) contains both molybdenum in the metallic state and molybdenum oxides. The ratio between the electrolysis products depends on the temperature of solution: a decrease in the temperature leads to an increase in the amount of metallic molybdenum.

     

Low-Temperature Reactions of α-Bromopropanoyl Chloride with Lithium Derivative of Ethyl Acetate

The reaction of 2-bromopropanoyl chloride with lithium ethyl acetate generated in situ by the reaction of equimolar amounts of lithium diisopropylamide with ethyl acetate forms, depending on the conditions (temperature, time, reagent ratio), diethyl 2,2′-(3-methyloxirane-2,2-diyl)diacetate, 2,2-dibromo-N,N-diisopropylpropanamide, and ethyl (5-methyl-4-oxo-4,5-dihydrofuran-2-yl)acetate as minor by-products along with the expected acylation product ethyl 4-bromo-3-oxopentanoate. The reaction with 2 or 5 equiv of lithium ethyl acetate (–78°C → –20°C) gave, together with the mentioned α-bromo ester, ethyl (5-methyl-4-oxo-4,5-dihydrofuran-2-yl)acetate formed as a result of transformations of the adduct of the second LiCH₂CO₂Et molecule and ethyl-4-bromo-3-oxopentanoate. The reaction 2-bromopropanoyl chloride with sodium malonic ester involves acylation of enol form of the primary expected acylation product to afford dimethyl |2-bromo-1-[(2-bromopropanoyl)oxy]propylidene-malonate.

     

Apparent Molar Volumes and Solvation Coefficients in Ternary-pseudo-binary Mixtures [（Styrene＋Ethyl Acetate or Benzene）＋（N-Methyl-2-pyrrolidone＋Ethyl Acetate or Benzene）]

Over the full range of compositions,in the ternary-pseudo-binary mixtures of x[(1-y)C6H5CH=CH2+ yCH3COOC2H5(or C6H6)]+(1-x)[(1-y)NMP+yCH3COOC2H5(or C6H6)],the apparent molar volumes of each pseudo-pure component at different y values were calculated from the density data at 298.15 K and atmospheric pressure.The results show that the four parameters cubic polynomial can correlate the apparent molar volume with the molar fraction well over the full molar fraction range.The limiting partial molar volumes and the molar volumes of each pseudo-pure component were evaluated with different methods.Based on the limiting partial molar volume and molar volume at a certain y value,a new universal coefficient termed as solvation coefficient γ was defined to describe quantitatively the solvation degree of pseudo-pure solute and the interactions of solute-solvent molecules from the macroscopical thermodynamics viewpoint.The results demonstrate the solvation coefficients decrease with the amount of the third component increasing for each pseudo-pure solute,irrespective of the pseudo-pure solvent.Then the solvation degrees of each pseudo-pure component,the specific interactions between the solute molecule and the solvent one were discussed in terms of the solvation coefficient.     

Solution Thermodynamics of Ethylhexyl Triazone in Some Ethanol + Ethyl Acetate Mixtures

Ethylhexyl triazone (EHT) is a sunscreen agent that is widely used in skin care product formulations, whose physicochemical properties have not been previously studied in detail. For this reason, solubility data were measured for EHT in ethanol (EtOH) + ethyl acetate (AcOEt) mixtures at five temperatures. By using the van’t Hoff and Gibbs equations, the thermodynamic functions: Gibbs energy, enthalpy, and entropy of solution, and of mixing, were evaluated from these solubilities. The solubility is greatest in mixtures with 0.10 and 0.20 mass fraction EtOH, but decrease as the EtOH mass fraction increases in the solvent mixtures. By means of an enthalpy-entropy compensation analysis, a nonlinear DH_soln⁰\Delta H_{\mathrm{soln}}^{0} versus DG_soln⁰\Delta G_{\mathrm{soln}}^{0} compensation plot was obtained having both negative and positive slopes as the solvent composition was varied. Accordingly to these results, it follows that the driving function for solubility of EHT is the entropy for solutions rich in EtOH or AcOEt, whereas in mixtures of medium composition, the driving function is the enthalpy.     

Isobaric Vapor–Liquid Equilibrium Data for the Quaternary System of sec-Butyl Acetate + sec-Butyl Alcohol + Dimethyl Sulfoxide + 1-Ethyl-3-methylimidazolium Acetate at 101.3 kPa

Journal of Solution Chemistry - The isobaric vapor–liquid equilibrium (VLE) data for the quaternary system sec-butyl acetate (SBAC)?+?sec-butyl alcohol...     

Thermo-Reversible Cellulose Micro Phase-Separation in Mixtures of Methyltributylphosphonium Acetate and γ-Valerolactone or DMSO

We have identified cellulose solvents, comprised of binary mixtures of molecular solvents and ionic liquids that rapidly dissolve cellulose to high concentration and show upper-critical solution temperature (UCST)-like thermodynamic behaviour - upon cooling and micro phase-separation to roughly spherical microparticle particle-gel mixtures. This is a result of an entropy-dominant process, controllable by changing temperature, with an overall exothermic regeneration step. However, the initial dissolution of cellulose in this system, from the majority cellulose I allomorph upon increasing temperature, is also exothermic. The mixtures essentially act as ‘thermo-switchable’ gels. Upon initial dissolution and cooling, micro-scaled spherical particles are formed, the formation onset and size of which are dependent on the presence of traces of water. Wide-angle X-ray scattering (WAXS) and ¹³C cross-polarisation magic-angle spinning (CP-MAS) NMR spectroscopy have identified that the cellulose micro phase-separates with no remaining cellulose I allomorph and eventually forms a proportion of the cellulose II allomorph after water washing and drying. The rheological properties of these solutions demonstrate the possibility of a new type of cellulose processing, whereby morphology can be influenced by changing temperature.     

Influence of Alkylammonium Acetate Buffers on Protein–Ligand Noncovalent Interactions Using Native Mass Spectrometry

We investigate the influence of three volatile alkylammonium acetate buffers on binding affinities for protein–ligand interactions determined by native electrospray ionization-mass spectrometry (ESI-MS). Four different types of proteins were chosen for this study. A charge-reduction effect was observed for all the cases studied, in comparison to the ions formed in ammonium acetate solution. When increasing the collision energy, the complexes of trypsin and the ligand were found to be more stable when sprayed from alkylammonium acetate buffers than from ammonium acetate. The determined dissociation constant (K_d) also exhibited a drop (up to 40%) when ammonium acetate was replaced by alkylammonium acetate buffers for the case of lysozyme and the ligand. The prospective uses of these ammonium acetate analogs in native ESI-MS are discussed in this paper as well.

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Graphical Abstract ?

     

Synthesis of an Anionic Receptor Based on Phenylhydrazone Group and Its Recognition Property for Acetate

A colorimetric anion receptor was synthesized by a simple method where the phenylhydrazone moiety was need as binding sites. The anion recognition via hydrogen-bonding interactions can be easily monitored by anion complexation induced changes in UV-vis absorption spectra. Moreover, the hydrogen bond formation between the phenylhydrazone N-H and acetate or fluoride anion was described on the basis of ^1H NMR experiments.     

Synthesis and Crystal Structure of an Acetate Radical Bridged Dinuclear Copper（ Ⅱ ） Complex

A new acetate radical bridged dinuclear copper(Ⅱ ) complex (C8H9NO2)2-Cu2(CH3COO)4 has been synthesized by the reaction of Cu(OAc)2 with pyridine-3-ethyl formate and further characterized by X-ray single-crystal diffraction. Crystal data for the title compound: triclinic system,space group P1,with a=8.1654(14),b=9.7010(16),c=9.9005(17) ,α= 83.266(2),β=78.887(2),γ=72.881(2)o,V=733.9(2) 3,Mr=665.58,Z=1,Dc=1.506 g/cm3,F(000)=342,μ=1.510 mm-1,the final R=0.0392 and wR=0.1005. According to the structural determination,each unit of the title compound is composed of two Cu(Ⅱ) atoms,two pyridine-3-ethyl formate molecules and four acetate ions. Each Cu(Ⅱ) coordinates to oxygen atoms of acetate and nitrogen atoms of pyridine-3-ethyl formate ligand to give a six-coordinate distorted octahedral geometry. It is worth mentioning that strong Cu–Cu bond can be observed in the title compound.     

Vibration-driven Reduction of CO2 to Acetate with 100 % Selectivity by SnS Nanobelt Piezocatalysts

Converting CO₂ into high-value C2 chemicals such as acetate with high selectivity and efficiency is a critical issue in renewable energy storage. Herein, for the first time we present a vibration-driven piezocatalysis with tin(II) monosulfide (SnS) nanobelts for conversion of CO₂ to acetate with 100 % selectivity, and the highest production rate (2.21 mM h⁻¹) compared with reported catalysts. Mechanism analysis reveal that the polarized charges triggered by periodic mechanical vibration promote the adsorption and activation of CO₂. The electron transfer can be facilitated due to built-in electric field, decreased band gap and work function of SnS under stress. Remarkably, reduced distance between active sites leads to charge enrichment on Sn sites, promoting the C−C coupling, reducing the energy barriers of the rate determining step. It puts forward a bran-new strategy for converting CO₂ into high-value C2 products with efficient, low-cost and environment-friendly piezocatalysis utilizing mechanical energy.     

Synthesis and Crystal Structure of an Acetate Radical Bridged Dinuclear Copper(Ⅱ) Complex

A new acetate radical bridged dinuclear copper(Ⅱ ) complex (C8H9NO2)2-Cu2(CH3COO)4 has been synthesized by the reaction of Cu(OAc)2 with pyridine-3-ethyl formate and further characterized by X-ray single-crystal diffraction. Crystal data for the title compound: triclinic system,space group P1,with a=8.1654(14),b=9.7010(16),c=9.9005(17) ,α= 83.266(2),β=78.887(2),γ=72.881(2)o,V=733.9(2) 3,Mr=665.58,Z=1,Dc=1.506 g/cm3,F(000)=342,μ=1.510 mm-1,the final R=0.0392 and wR=0.1005. According to the structural determination,each unit of the title compound is composed of two Cu(Ⅱ) atoms,two pyridine-3-ethyl formate molecules and four acetate ions. Each Cu(Ⅱ) coordinates to oxygen atoms of acetate and nitrogen atoms of pyridine-3-ethyl formate ligand to give a six-coordinate distorted octahedral geometry. It is worth mentioning that strong Cu–Cu bond can be observed in the title compound.     

Synthetic Features and Mechanism for the Preparation of Vinyl Chloride-co-Butyl Acrylate-co-Vinyl Acetate Terpolymer via Precipitation Polymerization

Without any type of su rfactant or dispersing agent,precipitation polymerization has great superiorities in both polymer synthesis and applications.In the present work,the polymerization of vinyl chloride(VC),n-butyl acrylate(BA),and vinyl acetate(VAc) are conducted in the precipitation polymerization system and series of their random terpolymers poly(vinyl chloride-co-n-butyl acrylate-co-vinyl acetate)(PCBV) are synthesized successfully.The effects of various polymerization conditions,including...     

Regioselective Synthesis of α‐Iodoacetates from Alkenes/Ammonium Acetate/I2 by Woodward's Reaction

Abstract

Regioselective synthesis of α‐iodoacetates from alkenes, ammonium acetate, and iodine in acetic acid is reported. The reaction is facile, fast, environmentally, friendly, and cost effective. α‐Iodoacetates are obtained from both acyclic and cyclic alkenes in high yields ranging from 80–95% within 10–20 min.